Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is

$6{\mathrm{Fe}}^{2+}+{\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}+14{\mathrm{H}}^{+}⟶6{\mathrm{Fe}}^{3+}+2{\mathrm{Cr}}^{3+}+7{\mathrm{H}}_2\mathrm{O}$

                      ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}⟶2{\mathrm{Cr}}^{3+}$

x-factor = 6

$\text{ Mohr's salts }{\mathrm{FeSO}}_4·{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4·6{\mathrm{H}}_2\mathrm{O}$

$\text{ Oxidation, }{\mathrm{Fe}}^{2+}⟶{\mathrm{Fe}}^{3+}$

x-factor = l mole ratio is reverse of x-factor ratio.

Therefore, one mole of dichromate required = 6moles of Mohr's salt.